Pick or “plectrum” technique is at the very foundation of being able to play both rhythm and single notes with clarity and precision. At this stage you may wonder why the emphasis on small details? These details will ultimately be instrumental in creating a comfortable and effective attack which is at the very core of everything you will do moving forward.
In my teaching experience I have often had new students holding the pick with 3 fingers or at an odd angle. This will eventually lead to bigger and bigger problems so achieving a “proper” picking technique is very very important to your musical progress.
With that in mind make sure that you hold the pick firmly without too much pressure. Allow your wrist to roll and keep your fore-arm totally relaxed. Begin with simple exercises like playing 4 attacks of each string using only a down stroke while striving for a nice even and pronounced volume. Think of the pick as an extension of your index finger as well as an extension of your arm thus forming a straight line from the fore-arm to the tip of the pick.
At this stage just let the pick push through the strings both in groups and single strings. Use a “rest stroke”, letting the pick come to rest on adjacent strings when playing only single notes.